PVA membrane filled β-cyclodextrin for separation of isomeric xylenes by pervaporation

Polyvinyl alcohol (PVA) membrane filled beta-cyclodextrin (beta-CD) was prepared by casting an aqueous solution of PVA and beta-CD oligomer. The membrane was crosslinked with glutaraldehyde for one hour. The weight content of beta-CD in the membrane was 33%. The membrane was used for separation of p-xylene/m-xylene mixture by pervaporation. Based on the experiments of sorption equilibrium, the solubility and the diffusion coefficient of the permeates in the membrane was obtained. Compared with PVA membrane, the solubilities of pure p-xylene and m-xylene in PVA membrane filled P-CD increased from 0.92, 0.78 to 10.4, 2.6 g (xylene)/100 g (dried membrane), respectively, and the solubility selectivity S-p/S-m increased from 1.18 to 4.0. Also, the diffusion coefficients of p-xylene and m-xylene decreased from 8.45 x 10(-12), 8.23 x 10(-12) to 6.83 x 10(-12), 7.23 x 10(-12) m(2)/s, respectively, and diffusion selectivity decreased from 1.03 to 0.94. These effects of beta-CD can be interpreted in terms of the inclusion strength in the cavity. The pervaporation performance of the PVA membrane filled beta-CD was investigated. A separation factor of 2.96 and a permeation rate of 95 g/m(2) h through the beta-CD filled PVA membrane for a 10 wt.% feed p-xylene concentration were obtained at 25 degrees C. The results indicated that PVA membrane filled beta-CD effectively improved the pervaporation performance, especially on the separation factor. (C) 2000 Elsevier Science S.A. All rights reserved.